Variability in a fjord-like coastal estuary I: Quantifying the circulation using a formal multi-tracer inverse approach

During 2002-2005, a comprehensive set of observations covering physical, biological, radiative and atmospheric parameters was obtained from the southern Strait of Georgia (SoG), Western Canada by the STRATOGEM program. Monthly time series of estuarine layer transports over 2002-2005 were estimated using a time-dependent 2-box model in a formal inverse approach. The formal inverse approach builds up upon a so-called ``pseudo-inverse{''} and the Singular Value Decomposition methodology. The transports are then consistent with the temperature and salinity fields, as well as riverine freshwater inflow (R) and detailed atmospheric heat fluxes. Uncertainty was analyzed by resampling observations using bootstrap methods. Analysis of these time series suggests that the SoG estuarine circulation is not very sensitive to the seasonal changes of R. Comparison of the surface layer transport (U1) and R yields the first observational relationship between the SoG estuarine circulation and R. The analysis of this relationship shows that U1 has a fractional form as R to the power of 1/n with n < 1. Such fractional relationship shows that the flows change only slightly with the freshet A 5-fold change in R results only in a 40% change in U1. However, freshwater range and uncertainty in the data prevented us from dearly determining the fraction n. Analysis of the transports in light of the residuals in the mass, heat and salt budgets suggests that our inversion procedure works properly and improves on the SVD inverse procedure. Analysis of the transports sensitivity to inversion parameters shows that the transports are close to both the a priori and true transports and that they are dependent on both a priori information and data. (C) 2013 Elsevier Ltd. All rights reserved.